1 6 Introduction to Botany. 



mixture of one third beeswax and two thirds rosin, taking 

 care to center the dish with the hour-hand spindle. Pack 

 moist pine sawdust into the dish, level with the surface, and 

 press soaked grains of corn into the sawdust, not very 

 tightly, broad face down, but do not cover them with the 

 sawdust. Put on the cover of the Petri dish, and hold it 

 in position by means of clips made of spring brass wire. 

 (See Figs. 7 and 8.) Wind the clock and set it in its nor- 

 mal position ; that is, with the hour-hand spindle horizontal. 

 Prepare seeds in another dish in exactly the same manner, 

 but fasten it so that it will stand vertically on its edge. 



In the first experiment the directive effect of gravity 

 will be neutralized by the revolution of the dish, while in 

 the second, gravity may exercise its usual influence on the 

 direction taken by root and shoot. Since the seeds are 

 not covered by the sawdust, their progress in germination 

 may be observed at any time without interrupting the 

 experiment. The position occupied by the parts of the 

 seedlings can easily be recorded for any period, by tracing 

 with ink on the cover immediately over them. 



DISCUSSION. 



5. Nature and Purpose of Seeds. — A seed is essentially 

 a young plant produced sexually by a flower (see page 168). 

 The young plant has temporarily ceased to grow, and 

 has been, or is to be, cast off from the parent plant, 

 having first been provided with reserve food materials 

 necessary to the resumption of growth, and with certain 

 means of protection. The purpose of the seed is to 

 insure the continuation, multiplication, and locomotion or 

 distribution of the species. Many plants are too tender to 

 survive the cold of winter, or the dry seasons of those 

 regions where the rain does not fall for many months of 



